Nano-fabrication involves the fabrication of very small structures, e.g., having features on the order of nanometers or smaller. One area in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.
An exemplary nano-fabrication technique is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as United States Patent Application Publication No. 2004/0065976, entitled “Method to Arrange Features on a Substrate to Replicate Features having Minimal Dimensional Variability;” United States Patent Application Publication No. 2004/0065252, entitled “Method of Forming a Layer on a Substrate to Facilitate Fabrication of Metrology Standards;” and U.S. Pat. No. 6,936,194, entitled “Functional Patterning Material for Imprint Lithography Processes,” all of which are incorporated by reference herein in their entirety.
The imprint lithography techniques disclosed in the aforementioned publications and patent include forming a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be positioned upon a motion stage to obtain a desired position to facilitate patterning thereof. To that end, a template is employed spaced-apart from the substrate with a formable fluid composition present between the template and the substrate. The fluid composition is polymerized to form a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the composition. The template is then separated from the solidified layer such that the template and the substrate are spaced-apart. The substrate and the solidified layer are then subjected to processes to transfer, into the substrate, a relief image that corresponds to the pattern in the solidified layer.
Spin coating techniques are sometimes used to form a layer of polymerizable material on a substrate before imprinting. However, the layer that results from spin coating can yield a non-uniform residual layer after imprinting, for example, if the template feature density is non-uniform. Furthermore, spin coating techniques can result in particle contamination of at least one side of a substrate (e.g., a wafer) if double-sided imprinting is needed.
Drop-on-demand dispensing methods can be used to form liquid layers on a substrate that result in a more nearly uniform residual layer after imprinting. However, gases trapped in the interstitial regions between drops of polymerizable liquid on the substrate can inhibit spreading and coalescence of the drops on the substrate. Defects such as interstitial voids can result in the polymerized layer when the polymerizable material forms a non-continuous layer on the substrate before imprinting. The amount of time required to expel gas from the interstitial regions can reduce throughput of an imprint lithography process.
Spin coating and drop-on-demand methods can include adding a surfactant to a polymerizable material to enhance release performance from a template. Additionally, at the fluid spread front, the surfactant can interact with the substrate. In some cases, the presence of a surfactant can limit the spreading of the material through, for example, a pinning effect.